1. Field of the Invention
The present invention relates to a semiconductor device and a manufacturing method thereof, and particularly relates to a semiconductor device having improved heat radiation properties and a manufacturing method thereof.
2. Description of the Prior Art
As to circuit devices set in electronic equipment, reduction in size, thickness and weight thereof has heretofore been demanded for adoption thereof in portable telephones, portable computers and the like. In order to satisfy these conditions, a semiconductor device called a CSP (Chip Scale Package) has been developed, which has the same size as that of a semiconductor element to be built thereinto.
Among the CSPs, there is a particularly small WLP (Wafer Level Package). With reference to FIGS. 6A to 6C, a method for manufacturing the WLP will be schematically described. This technology is described for instance in Japanese Patent Application Publication No. 2004-172542.
With reference to FIG. 6A, first, a number of semiconductor device parts 102 are formed on a semiconductor wafer 100. In each of the semiconductor device parts 102, as transistor and the like are formed by a diffusion step. Moreover, on an upper surface of each of the semiconductor device parts 102, electrodes 101 are formed, which are connected to elements inside a substrate. Furthermore, an insulating layer 101 is formed in a state where upper parts of the electrodes 103 are exposed. On an upper surface of the insulating layer 101, wirings 104 are patterned. Furthermore, the upper surface of the insulating layer 101 is covered with a covering layer 110 so as to cover the wirings 104. Moreover, openings are provided in the covering layer 110 in regions where external electrodes 105 are to be formed. Furthermore, the external electrodes 105 made of, for example, solder or the like are welded to upper surfaces of the wirings 104. A rear surface of the semiconductor wafer 100 having such a configuration is attached to an upper surface of a dicing sheet 106.
With reference to FIG. 6B, next, the semiconductor device parts 102 are separated from each other by using a rapidly rotating blade 107 to cut the wafer 100. The semiconductor wafer 100 and the insulating layer 101 are completely cut by the blade 107. The separated semiconductor device parts 102 become semiconductor devices, respectively.
FIG. 6C shows a cross-section of a semiconductor device 108 manufactured by the above steps. It is clear from FIG. 6C that a planar size of the semiconductor device 108 is approximately the same as that of a semiconductor substrate 109. The planar size of the semiconductor device 108 is, for example, about 5 mm×5 mm, which is very small.
However, in recent semiconductor devices, an operating frequency is increased for high-speed signal processing, and a heat release value is increased. Meanwhile, in the semiconductor device described above, since the size of the entire device is small, a surface area thereof is too small to obtain sufficient heat radiation properties. Accordingly, problems such as characteristic deterioration and destruction have occurred due to a rapid increase in a temperature of the semiconductor device along with operations thereof.
As a method for solving the above problems, there is a method far releasing heat from the semiconductor device through conductive patterns formed to be partially wide on a mounting substrate side on which the semiconductor device is mounted. However, by use of the above method, the conductive patterns on the mounting substrate side are formed to be wide. Then, an area of the mounting substrate, which is practically required for mounting the semiconductor device, is increased. As a result, there is a problem that packaging density is lowered.
Furthermore, in the manufacturing method described above, chipping occurs in the dicing step using the blade. As a result, there is a problem that a crack is generated in the semiconductor substrate 109 of each of the semiconductor device parts 102. If this crack is large, characteristics of the semiconductor device are deteriorated to cause failures. Moreover, even if the crack is small, there is caused no performance failure. However, in the case where the semiconductor device 108 is the WLP, sides of the semiconductor substrate 109 are exposed to result in poor appearance.